1. Field of the Invention
The present invention relates generally to valves for controlling the flow of fluids under pressure. More particularly, the invention concerns a novel valve assembly and the method of making the same in which, in the open position, fluid flows from the inlet port of the valve assembly into a very narrow annular passageway formed in a cylindrically shaped valve slide member, or spool, thence through a plurality of axially extending passageways formed internally of the slide member and finally into the outlet port of the valve assembly.
2. Discussion of the Prior Art
Numerous types of valve assemblies embodying reciprocally movable slide members exist for controlling the flow of fluids under pressure. These valves may be provided with valve bodies and spools of widely varying configurations and may be pressure or solenoid operated, or they may be operated by pyrotechnic, mechanical or electromechanical devices of specialized design. Similarly, these prior art valve assemblies may embody pressure ports and closure means of widely varying design. However, typical of most prior art valve assemblies of this class, elastomeric O-rings, or comparable sealing devices, are used to prevent undesired flow of fluid between the slide member and the valve body as the slide member is reciprocated. Exemplary of various of the more sophisticated prior art valve designs are those disclosed in U.S. Pat. Nos. 2,971,090 and 3,731,905 issued to the present inventor.
Almost without regard to the particular design features found in a given prior art spool type valve assembly, either the valve body or the spool is stepped or ported to provide a fluid flow path through the valve assembly. While typically the valve body is ported or stepped, in some special purpose applications the spool or poppet may also be stepped. In either case, precision fabrication of valve assemblies of this character is difficult and often quite expensive. Additionally, because there must always be relative movement between the slide member and the valve body, and, accordingly, relevant movement between one or the other of these parts and the sealing means employed, as, for example, one or more elastomeric O-rings, some wear of the sealing means must be expected. In these instances where the O-ring, or other elastomeric sealing means, is repeatedly brought into engagement with a pronounced step, port, flange, or shoulder formed in the valve assembly, substantial damage to the sealing means will unavoidably occur as a function of time. Such wear seriously effects the reliability of the valve and results in continuous and costly maintenance and system downtime.
The unique valve assembly of the present invention effectively overcomes the aforementioned drawbacks of prior art valves by providing a novel, perfectly cylindrical slide member or spool which has internally disposed fluid passageways. During the operation of the valve, this unique slide member engages the sealing means of the valve assembly in a manner so as to virtually eliminate wear on the sealing means. Additionally, because the spool is precision ground to a uniform diameter over its entire length, there exists no differing diameters or steps which might abrade the sealing means or tend to cause an inadvertent shifting of the spool within the valve body due to fluid pressures exerted thereon. Further, because the fluid being controlled by the valve flows internally of the spool, widely varying flow rates can be readily achieved merely by adjusting the spool diameter and the size and number of the internal passageways formed within the spool.
As will be more clearly understood from the description which follows, the present invention enables the cost effective manufacture of precision, high pressure valves which require minimum maintenance, are highly reliable in operation and provide great versatility in use.